Terminal construction



Sept. 17, 1957- J. R. CONRAD TERMINAL CONSTRUCTION 2 Shets-Sheet 1 INVENTOh. Joiz/z E. Kara/"ad; W W

Filed Sept. 21, 1955 Sept. 17, 1957 J. R. CONRAD TERMINAL CONSTRUCTION I 2 Sheets-Sheet 2 m z a r a I p 1.4.

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m 7 JJ m 4 7 m 2% v United States Patent TERMINAL CONSTRUCTION John R. Conrad, Glencoe, Ill., assignor to S & C Electric Company, Chicago, Ill., a corporation of Delaware Application September 21, 1955, Serial No. 535,633

4 Claims. (Cl. 200-115.5

This invention relates, generally, to terminals for high voltage electrical devices and it has particular relation to the construction of terminals for high voltage fuse tubes. It constitutes an improvement over the terminal shown in U. S. Patent No. 2,531,949, issued November 28, 1950.

The terminal construction as shown in this patent for the lower end of an expulsion fuse tube of a bayonet type fuse cutout is adapted to receive fuse links having flexible leads both with and without rigid anchor members or cone terminals thereon. For this purpose a bifurcated threaded extension is provided in the patent on the lower end of the terminal. When a fuse link having only a flexible lead is used, the latter is positioned along the bottom of the slot between the arms of the threaded extension and a clamp nut, which has a clamp jaw that is movable in the slot together with the nut, clamps the flexible lead between it and the bottom of the slot. When a fuse link provided with a rigid anchor member or cone terminal is used, the clamp nut is dispensed with and the anchor member bears against the lower ends of the arms of the threaded extension.

Certain difliculties and disadvantages have been encountered in the use of the terminal construction just outlined. Because of space limitation, it is not possible to employ a construction in which the arms of the extension have a cross-section sufficient to provide the desired rigidity. They are readily deflected on application of slight force and the nut, when used, tends to become loosened. When the anchor member or cone terminal type of fuse link is employed, the arms provide two current paths which are likely to be of unequal resistance as contact resistance grows in service under adverse conditions. Experience indicates that the current flow may then take place mainly through one of the arms with the result that its temperature may become excessive, leading to eventual destructive overheating.

Accordingly, among the objects of this invention are: To provide a terminal for the lower end of an expulsion fuse tube of the bayonet type that will overcome the foregoing difiiculties and disadvantages; to provide more adequate and dependable current carrying ability for the terminal; to increase substantially the cross-section of the threaded extension to which a clamp nut is applied and still permit the connection of either a flexible lead or an anchor member thereto; and to employ a tubular threaded extension having a slot therein closed on three sides, adapted to receive the anchor member or cone terminal therein to bear against the outer end and to have the flexible lead wrapped around its outer surface and clamped by a nut on the tubular threaded extension against a grooved or knurled Wall portion at its base thereby providing increased clamping action for the flexible lead resulting in a greater mechanical security and improved electrical contact.

Other objects of this invention will, in part, be obvious and in part appear hereinafter.

This invention is disclosed in the embodiment thereof 2,806,919 .Patented Sept. 17, 1957 shown in the accompanying drawings and it comprises the features of construction, combination of elements and arrangement of parts that will be exemplified in the construction hereinafter set forth and the scope of the application of which will be indicated in the ap ended claims.

For a more complete understanding of the nature and scope of this invention reference can be to the following detailed description, taken together with the accompanying drawings, in which:

Figure 1 is a View, in side elevation and at a reduced scale, of a bayonet type expulsion fuse device in which the present invention is embodied;

Figure 2 is a longitudinal sectional view at full scale of an expulsion fuse tube for the bayonet type cutout shown in Figure 1 having the terminal at the lower end constructed in accordance with this invention;

Figure 3 is a cross-sectional view, on an enlarged scale, and taken generally along the line 3-3 of Figure 2 and showing not only the terminal at the lower end of the fuse tube but also the terminal in the insulating housing and a portion of the latter;

Figure 4 is a view, similar to Figure 2, showing how a fuse link having an anchor member or cone terminal on the flexible lead can be applied to the new terminal;

Figure 5 is a view, in side elevation and at an enlarged scale, of the improved terminal;

Figure 6 is a view, in front elevation, of the terminal shown in Figure 5;

Figure 7 is a bottom plan view of the terminal shown in Figure 5;

Figure 8 is a view, in side elevation, of the clamp nut that is employed in connection with the terminal shown in Figures 57;

Figure 9 is a top plan view of the nut shown in Figure 8; and

Figure 10 is a cross-sectional view of the nut shown in Figure 8.

Referring now particularly to Figure 1 of the drawings, it will be observed that the reference character 10 designates, generally, a bayonet type cutout such as that shown and described in more detail in U. S. Patent No. 2,108,993. The cutout 10 is arranged to be mounted on a cross arm 11 or like support. For this purpose a clamp 12 may be provided which supports the cutout 10 by means of a bracket 13. The cutout 10 includes a corrugated tubular body or housing 14 of insulating material such as porcelain.

The cutout 10 also includes a handle 15 of insulating material, such as porcelain, and it is arranged to be threaded onto a terminal 16 which is located at the upper end of a fuse tube 17. As shown in Figure 2 the fuse tube 17 is formed of insulating material. For example, it may have a linear of fiber and an outer covering of a phenolic condensation product. In Figure 2 of the drawings the parts are shown full size. However, it will be understood that this is for illustrative purposes only and that various sizes and dimensions can be employed depending upon the operating conditions.

Within the fuse tube 17 there may be located a fuse link which is indicated, generally, at 20. The fuse link 20 may be of the type shown in U. S. Patent No. 2,108,993, although it will be understood that other types of fuse links can be employed in practicing this invention. At its upper end the fuse link 20 has a head assembly 21 which bears against the upper end of the terminal 16 to provide electrical and mechanical connection therewith. The fuse link 20 has a flexible conductor 22 extending from its other end. The flexible conductor 22 comprises a large number of small diameter wires of good conducting material such as copper.- It extends downwardly through the hereof the fuse tube 17 and out 'at the lower discharge end where a terminal, shown generally at 23, is located. The terminal 23 includes a ferrule 24 which is arranged, as shown, to receive the lower end of the fuse tube 17. A pin 25 serves to hold the ferrule 24 in place on the lower end of the fuse tube 17.

In Figure 3 of the drawings the construction of the terminal 23 is illustrated at double the scale used in Figure 2. It will be observed that the terminal 23 includes a semi-circular tongue 26 which extends downwardly from and is integrally formed with the ferrule 24. At the lower or outer end of the tongue 26 is a wall portion 27 which is provided with a central slot 28 on the front side and with a radially outwardly projecting portion 29 on the rear side. The portion 29 is formed by thickening the lower end of the tongue 26 to provide additional material and a clamping surface against which the flexible conductor 22 can be clamped as will be described hereinafter.

Projecting from the wall portion 27 is a tubular extension 32 which has a central opening or slot 33 that constitutes an extension of the central slot 28. The combination of the slot 28 and the opening 33 provides a rectangular slot closed on three sides as shown more clearly in Figure 7 of the drawings. The front portion of the tubular extension 32 is slabbed off to provide flat faces 34 for the purpose set forth in Patent No. 2,531,949 above referred to.

The tubular extension 32 has external threads 35 that are arranged to receive a clamp nut 36 which is provided with threads 37, as shown in Figure 10, on the inside.

Extending diagonally across the wall portion 27 and to one side of the tubular extension 32, as shown more clearly in Figure 6, is a slot 38 which is provided for receiving the lower end 39 of the flexible conductor 22 whence it may be wrapped around the tubular extension 32 as shown in Figure 2.

When a fuse link 20 is employed, as shown in Figure 2, the same is inserted through the upper open end of the fuse tube 17 and the flexible lead projects out of the lower open end through the terminal 23. The lower end 39 of the flexible lead 22 is placed in the diagonal slot 38 in the wall 27 and then is wrapped around the tubular extension 32 as shown in Figure 2. Thereafter the nut 36 is threaded onto the tubular extension 32 and the nut 36 is tightened to clamp the lower end 39 of the flexible lead 22 between the upper surface of the nut 36 and the lower or outer surface of the wall portion 27. Thereafter the surplus end portion indicated at 40 by broken lines in Figure 3 is cut off.

With a view to more securely holding the flexible lead 22 and increasing the clamping effect that is obtained between the nut 36 and the lower surface of the wall portion 27 the latter is provided with ribs 41 and intervening grooves 42 as shown more clearly in Figures 6 and 7 of the drawings. Complementary ribs 43 and grooves 44 are provided on the upper surface of the nut 36 as shown in Figures 9 and 10. This construction provides ample contact surface with the lower end 39 of the flexible lead 22 and a secure anchorage. A corrugated or knurled surface can be employed instead of the ribs 41 and grooves 42, as will be understood readily, for cooperating with the nut 26 provided with the ribs 43 and grooves 44. I

From Figure 4 of the drawings it will be observed that the present invention is adapted for use in an expulsionfuse construction employing a spring and cable assembly that is indicated, generally, at 47. This assembly includes a head 48 that bears against the upper end of the terminal 16 at the upper. end of the fuse tube 17. The fuse link 20 is connected by means (not shown) to the-upper end of the fuse link 20. Here the fuse link 20 has a. rigid anchor member or cone terminal 49 applied to the flexible lead 22 and it has a wedge portion 50 which is arranged to bear against the lower end 51 of the tubular extension 32. It will be observed that the rigid anchor member or cone terminal'49 fits readily into the central slot 28 provided in the wall portion 27 and also in the opening 33 through the tubular extension 32.

At the lower end of the rigid anchor member or cone terminal 49 is an indicator 52 which may be employed to indicate that the fuse link 20 has not blown. When the fuse link 20 blows, it will be understood that the indicator 52 will drop to the ground.

The opposite sides of the opening or three sided slot through the tubular extension 32 are recessed at 53, Figure 3, for accommodating the wedge portion 50 of the rigid anchor member or cone terminal 49.

In operation, the spring and cable assembly 47 with the fuse link 26, constructed as shown in Figure 4, is inserted through the terminal 16 at the upper end of the fuse tube 17. The indicator 52 projects from the lower end of the fuse tube 17 sufficiently far to permit it to be grasped and to tension the spring and cable assembly 47 by withdrawing the fuse link 20 downwardly through the fuse tube 17. It is drawn sufficiently far to permit the rigid anchor member or cone terminal 49 to be inserted in the slot or opening 33 in the tubular extension 32 and the wedge portion 50 to engage against the lower or outer end 51 of the tubular extension 32.

It will be observed now that the terminal 23 can be employed either with a fuse link 20 having only the flexible lead or conductor 22 extending therefrom, as shown in Figure 2, or with the fuse link 20, as shown in Figure 4, with the rigid anchor member or cone terminal 49 secured to the flexible conductor or lead 22.

' By providing the relatively large contact area on the lower side of the wall portion 27 and on the upper side of the clamp nut 36, it is possible to provide an exceptionally low resistance connection between the terminal 23 and the flexible lead 22. When the tubular extension 32 is called upon to conduct current to the rigid anchor member or cone terminal 49, Figure 4, there is only a single current path thereto and there is no likelihood of current division along parallel paths. The reason for this, of course, is that the extension 32 is tubular and the opening 33 therethrough is closed on three sides.

When a fuse link of the type shown in Figure 2 is employed with the spring and cable assembly 47, as shown in Figure 4, the flexible conductor 22 can be securely mechanically gripped between the nut 36 and the wall portion 27 after it has been wrapped or snubbed around the tubular extension 32. The relatively high tension force applied by the spring of the spring and cable assembly 47 is readily restrained by the clamping action applied by the nut 36 as long as the fuse link remains intact.

Since certain changes can be made in the foregoing construction and different embodiments of the invention can be made without departing from the spirit and scope thereof, it is intended that all matter shown in the accompanying drawings and described hereinbefore shall be interpreted as illustrative and not in a limiting sense.

What is claimed as new is:

l. A terminal for use at the discharge end of an expulsion fuse tube and arranged to have connected thereto flexible conductors of replaceable fuse links with or without rigid anchor members thereon comprising, a ferrule for receiving one end of the fuse tube, a tongue having a semicircular cross section extending from said ferrule away from its end which receives the fuse tube and a wall portion across the outer end having a central slot, an externally threaded tubular extension formed integrally with and projecting outwardly from said wall portion with the opening therethrough constituting an extension of said slot and with a portion slabbed off to provide a continuation of said slot closed on three sides for admitting a rigid anchor contact member to bear on its outer end or for receiving a nut to clamp a flexible conductor wrapped around said tubular extension against said wall portion the diameter of said threaded tubular extension being substantially less than the width of said tongue whereby said wall portion is provided thereon, and a nut on said threaded extension for clamping the flexible conductor against said wall portion.

2. A terminal for use at the discharge end of an expulsion fuse tube and arranged to have connected thereto flexible conductors of replaceable fuse links with or without rigid anchor members thereon comprising, a ferrule for receiving one end of the fuse tube, a tongue having a semi-circular cross section extending from said ferrule away from its end which receives the fuse tube and a wall portion across the outer end 'having a central slot, and an externally threaded tubular extension formed integrally with and projecting outwardly from said wall portion with the opening therethrough constituting an extension of said slot and a portion slabbed off to provide a continuation of said slot closed on three sides for admitting a rigid anchor contact member to bear on its outer end or for receiving a nut to clamp a flexible conductor wrapped around said tubular extension against said wall portion, the outer surface of said wall portion having a roughened surface around said tubular extension against which said flexible lead can be clamped by said nut threaded on said tubular extension.

3. A terminal for use at the discharge end of an expulsion fuse tube and arranged to have connected thereto flexible conductors of replaceable fuse links with or Without rigid anchor members thereon comprising, a.

ferrule for receiving one end of the fuse tube, a tongue having a semi-circular cross section extending from said ferrule away from its end which receives the fuse tube and 35 a wall portion across the outer end having a central slot, and an externally threaded tubular extension formed integrally with and projecting outwardly from said wall portion with the opening therethrough constituting an extension of said slot and a portion slabbed off to provide a continuation of said slot closed on three sides for admitting a rigid anchor contact member to bear on its outer end, said wall portion on one side of said tubular extension having a slot for receiving a flexible conductor to be wrapped around said extension and clamped by a nut threaded thereon against said wall portion.

4. A terminal for use at the discharge end of an expulsion fuse tube and arranged to have connected thereto flexible conductors of replaceable fuse links with or without rigid anchor members thereon comprising, a ferrule for receiving one end of the fuse tube, a tongue having a semi-circular cross section extending from said ferrule away from its end which receives the fuse tube and a wall portion across the outer end having a central slot and a radially outwardly projecting portion, and an externally threaded tubular extension formed integrally with and projecting outwardly from said wall portion with the opening therethrough constituting an extension of said slot and a portion slabbed off to provide a continuation of said slot closed on three sides for admitting a rigid anchor contact member to bear on its outer end, said wall portion on one side of said tubular extension having a slot for receiving a flexible conductor to be wrapped around said extension, the outer surface of said wall portion having rib and groove means generally concentric with said tubular extension against which said flexible lead can be clamped by a nut threaded on said tubular extension.

References Cited in the file of this patent UNITED STATES PATENTS 883,201 Johnson Mar. 31, 1908 2,091,453 Ramsey Aug. 31, 1937 2,108,993 Ramsey Feb. 22, 1938 2,531,949 Schultheiss Nov. 28, 1950 

